The present invention relates to a motor-driven compressor including an injection port that draws intermediate pressure refrigerant into a compression chamber formed by the engagement of a fixed scroll and a movable scroll.
Japanese Laid-Open Patent Publication No. 2003-120555 describes a motor-driven scroll compressor in which an injection pipe is connected to an injection port of a compression chamber. A vapor-liquid separator is connected to the injection pipe. The injection pipe includes a check valve. In a refrigeration cycle, the check valve opens the injection pipe during a high load operation (e.g., heating operation) and closes the injection pipe during a low load operation (e.g., cooling operation). During the high load operation of the refrigeration cycle, an intermediate pressure gaseous refrigerant separated by the vapor-liquid separator is injected into the compression chamber through the injection pipe, which is open through the check valve, and the injection port. This increases the amount of the gaseous refrigerant drawn into the compression chamber and improves the performance of the motor-driven compressor during the high load operation of the refrigerant cycle.